The invention relates to an endoscope having at least one light source and a passive cooling in order to lead away lost heat produced by the light source, in proximal direction.
The present invention relates in particular to a medical endoscope, which is used as a viewing instrument during minimal invasive surgery. In the case of a medical endoscope such as this, the elongated shaft is partially inserted into the body through an artificially created or natural opening.
Nowadays, endoscopes have one or more light sources which are integrated in the endoscope shaft and are in the form of light-emitting diodes (LEDs). The integration of one or more light sources in the shaft of the endoscope, normally in the distal area of the shaft, means that there is no need for any external light source, for example a xenon lamp. The advantage of one or more light sources which are integrated in the shaft of the endoscope is that there is no need for an optical waveguide which is required when using an external light source, thus improving the ergonomics of the endoscope. The lack of external light sources and optical waveguides also reduces the production and procurement costs of endoscopes.
However, an endoscope which has a light source integrated in the shaft is subject to the technical problem that the light source produces lost heat in its vicinity in the shaft during operation, which also heats the shaft severely, in particular in the area of the distal end of the shaft, where the light source or sources is or are arranged.
An endoscope which is used for surgery is subject to the regulations of medical product law. According to the medical product law, the outside of the endoscope shaft must not exceed a temperature of 41° C., in order to prevent heat-dependent damage being caused to tissue in the human or animal body.
However, modern high-power LEDs produce lost heat which is so great that the shaft would quickly rise above the required maximum temperature of 41° C. Against this background, it is necessary to provide cooling in the shaft, to lead away lost heat such that the shaft is not heated above the legally stipulated maximum temperature.
Various concepts are known for cooling or leading away the lost heat.
In the case of an endoscope that is known from US 2008/0151046 A1, which is an endoscope for industrial purposes for examining machines, in particular aircraft engines, a heat pipe whose distal end is thermally conductively coupled to the light source is provided for leading away the lost heat from the light source which is arranged in the distal area of the shaft and is in the form of an LED. A heat pipe such as this is a heat transmitter which uses the heat of vaporization of a substance which is contained in the heat pipe to allow a high heat flow density, that is to say large amounts of heat can be transported in a small cross-sectional area. No additional auxiliary power, such as a circulation pump, is required to circulate the substance which is provided as the heat transport medium in the heat pipe, thus minimizing the maintenance effort and operating costs of a heat pipe such as this.
In a heat pipe, the heat carrier medium is vaporized at the “warm” end of the heat pipe, with the vapour being passed to the “cold” end, where the vapour condenses again. Latent heat is therefore used for leading away heat, as a result of which the thermal conduction in a heat pipe is many times greater than the thermal conduction in, for example, copper. In the heat pipe, liquid which is used as the heat transport medium is fed back by means of capillaries to the vaporization end on the basis of the wicking principle. The condensed fluid therefore flows back to the vaporization end of the heat pipe in the capillary independently of the orientation, that is to say to that end of the heat pipe which is coupled to the light source. As a result of the use of the capillary principle, heat pipes therefore operate in any desired orientations with respect to the force of gravity.
In the case of the known endoscope mentioned above, the heat pipe extends proximally over a short length of the shaft of the endoscope, and a thermally conductive wire, for example a copper wire, is connected to the proximal end of the heat pipe, with the wire extending further proximally, and with its proximal end being thermally conductively connected to the inside of the shaft of the endoscope.
However, this type of cooling is insufficient for a medical endoscope, because the heat is transmitted from the heat pipe to the shaft of the endoscope, as a result of which the shaft is heated, what, however, is intended to be avoided in a medical endoscope.
DE 296 13 103 U1 discloses an endoscope for medical purposes, in the distal end of whose shaft light-emitting elements are arranged, with channels being provided in the shaft in order to pass a fluid through, for cooling.
JP 2007 007 321 A discloses an endoscope in the distal area of whose shaft a light source, which is in the form of an LED, is arranged, with a pipeline being laid in the shaft, for cooling or for leading away the lost heat from the LED, through which pipeline air is passed for cooling.
Further endoscopes, in which the cooling for the light source arranged in the shaft is provided by means of an external cooling circuit are known from JP 2007 229 261 A, JP 2007 007 322 and EP 1 738 679 A2.
In the known cooling concepts mentioned above, the endoscope shaft is therefore cooled by means of an external cooling circuit, with a cooling medium, for example a gaseous or liquid cooling medium, being passed through the shaft.
However, the disadvantage of a cooling concept such as this is that external cooling lines, circulation pumps and a reservoir for the cooling medium are required, for example, for the cooling circuit, which on the one hand increases the production effort and cost of an endoscope such as this, and on the other hand also adversely affects the ergonomics of the endoscope, because the endoscope must be connected to external cooling lines of the cooling circuit, which have a disturbing effect when the endoscope is being handled during a surgical procedure.